Add SerializeBatch method to the Serializer interface (#4107)

plugins/serializers/registry.go

@@ -25,6 +25,11 @@ type Serializer interface {
 	// separate metrics should be separated by a newline, and there should be
 	// a newline at the end of the buffer.
 	Serialize(metric telegraf.Metric) ([]byte, error)
+
+	// SerializeBatch takes an array of telegraf metric and serializes it into
+	// a byte buffer.  This method is not required to be suitable for use with
+	// line oriented framing.
+	SerializeBatch(metrics []telegraf.Metric) ([]byte, error)
 }
 
 // Config is a struct that covers the data types needed for all serializer types,
@@ -72,7 +77,7 @@ func NewSerializer(config *Config) (Serializer, error) {
 }
 
 func NewJsonSerializer(timestampUnits time.Duration) (Serializer, error) {
-	return &json.JsonSerializer{TimestampUnits: timestampUnits}, nil
+	return json.NewSerializer(timestampUnits)
 }
 
 func NewInfluxSerializerConfig(config *Config) (Serializer, error) {